The present invention relates to an ink jet recording apparatus comprising a carriage which travels in a widthwise direction of a recording sheet or the like; and a recording head mounted on the carriage for jetting ink droplets to record an image on the recording sheet in accordance with print data. Particularly, the present invention relates to a cleaning control technique which shortens a suction time required for maintenance of the recording head or for refilling the recording head with ink, and promotes removal of ink, whose viscosity has been increased, and air bubbles from an ink channel extending from an ink reservoir to the recording head.
Since owing to the development of personal computers graphic processing can be performed relatively easily, a demand exists for recording apparatuses that can, for example, output high quality hard copies of color images displayed on screens. In response to this demand, recording apparatuses in which ink jet recording heads are mounted are being produced. Since during printing the noise made by such ink jet recording apparatuses is relatively low, and since the apparatuses can deposit small dots at a high density, the apparatuses are presently being used to perform a variety of different types of printing, to include color printing.
Such an ink jet recording apparatus comprises: ink jet recording heads, for receiving ink from ink cartridges; and a paper feeding mechanism, for moving a recording sheet relative to the recording head. During the printing process, the recording heads, which are carried along by a carriage while it moves the width of a recording sheet, eject ink droplets that are deposited on the recording sheet. Mounted on the common carriage are a black recording head for ejecting black ink, and color recording heads for ejecting yellow, cyan and magenta inks, for example, so that not only can text be printed in black ink, but also full color printing can be performed by changing the ratio of the inks to be ejected.
Since the ink jet recording heads perform printing by pressurizing ink in a pressure generating chamber and then ejecting that ink through nozzles as ink droplets, a print failure can be caused by an increase in the viscosity of the ink or the solidification of the ink due to the evaporation of a solvent through nozzle orifices, by the attachment of dust particles, or by the entry of air bubbles.
Therefore, the ink jet recording apparatus further comprises a cap for sealing the nozzle orifices of the recording head while printing is not being performed, and a wiping blade for cleaning a nozzle plate as needed. The cap not only serves as a lid for protecting ink at the nozzle orifices from being dried out when printing is not being performed, but when the nozzle orifices are clogged, it also seals a nozzle plate and induces a flow of ink through the nozzle orifices so as to resolve an ink ejection failure that is caused by the clogging of the nozzle orifices due to the solidification of ink, or due to air bubbles that have entered an ink channel.
The forcible ink suction process, which is performed to prevent the clogging of the recording head or the entry of air bubbles into an ink channel, is normally called a cleaning operation. The cleaning operation is begun when printing is restarted after the apparatus has been halted for a long time, or when a user manipulates a cleaning switch to resolve the degrading of the quality of a recorded image. For this process, ink droplets are drawn out through the nozzle orifices by the application of a negative pressure, and the wiping blade, constituted by an elastic rubber plate, wipes the surface of the recording head.
The capping member also has a capability of discharging ink droplets by application to the recording head of a drive signal that is irrelevant to printing. This function is called a flushing operation. The flushing operation is performed at predetermined cycles for the purposes of: recovering meniscuses, which are irregularly formed in the vicinity of nozzle orifices of the recording head as a result of wiping action of the wiping blade during the cleaning operation; preventing mixture of colors, which would be removed by the capping member applying weak suction to the ink at the nozzle orifices; and preventing clogging in the nozzle orifices from which a small amount of ink droplets is ejected during a printing operation, which would otherwise be caused by an increase in the viscosity of ink.
There has recently been provided an ink jet recording apparatus which uses at least six colors of ink; that is, dark magenta, light magenta, dark cyan, light cyan, yellow, and black, in order to improve the quality of a print at the time of color printing.
The ink jet recording apparatus that uses multiple colors of ink requires at least six rows of nozzle orifices. In order to improve yield in the manufacturing processes and to simplify the sealing effected by the capping member, two recording heads are usually mounted on one carriage. Further, the capping member is provided with cap units for individually sealing the respective recording heads and two suction pumps for applying negative pressure to the respective cap units. The two suction pumps are connected to a paper feed motor by way of a joint mechanism which is brought into or out of contact with a paper feed mechanism according to the position of the carriage.
Although such a configuration enables a reduction in load imposed on the motor at the time of actuation of the pump, it disadvantageously requires much time for maintenance of the recording head or a built-in mechanism provided in the pumps for selecting between the two pumps according to the direction of rotation, which in turn results in complication of the structure of the pumps or renders the pumps bulky.
In order to greatly improve the resolution of an image recorded on the recording sheet, the number of nozzle orifices formed on each recording head tends to be increased more and more, or the diameter of the nozzle orifices tends to be reduced further. In the configuration of the ink jet recording apparatus, in which the individual recording heads are alternately sucked by means of a single suction pump, a deficiency arises in the suction capability of the pump.
For example, air bubbles, which have entered the ink channel in association with replacement of an ink cartridge, go on to enter the recording head, thereby resulting in ink ejecting failures.
In order to prevent the ink ejecting failures, the air bubbles are discharged from the inside of the recording head (i.e., a replacement cleaning operation is performed) simultaneous with suction and discharge of ink from the recording head. In a case where the flow rate of ink is lower than a predetermined flow rate as a result of a deficiency arising in the suction capability of the pumps, air bubbles present in the recording head remain caught within a complicated flow channel within the recording head. The replacement cleaning operation may result in mere consumption of ink but never ends in elimination of the air bubbles. For this reason, a flow rate faster than the predetermined flow rate must be achieved in order to sufficiently discharge the ink, whose viscosity has been increased, and air bubbles from the inside of the recording head. To this end, the suction capability of the pump must be increased greatly.
This type of recording apparatus generally employs, as a suction pump, a tube pump which generates negative pressure by sequentially squeezing a tube arranged in a circular-arch pattern through use of a roller, for the purpose of implementing an inexpensive suction pump, ensuring the operation of the suction pump, and preventing ink stains.
A conceivable measure to improve the suction capability of such a tube pump is to increase the number of rotations of the pump, as well as to increase the radius of the tube arranged in the circular-arch pattern.
However, if the number of rotations of the pump is increased, the number of times the tube is squeezed by the roller is increased, thus shortening the life of the pump. In contrast, if the radius of the tube arranged in the circular-arch pattern is increased, the outer diameter of the pump is inevitably increased. In this type of recording apparatus intended to be made compact, an extreme difficulty is encountered in determining the layout of such a pump, and therefore the designer encounters great difficulty in designing a product.
Generation of the fastest possible flow of ink within the ink channel between the ink reservoir; e.g., an ink cartridge, and nozzle orifices of the recording head is an effective measure for performing the previously-described cleaning operation. The fastest flow enables discharge of the air bubbles present within the flow channel to a certain extent together with removal of ink whose viscosity has been increased. Simultaneously, ink solids adhering to the vicinity of the nozzle orifices can also be removed. However, increasing the flow rate of ink during the cleaning operation requires an increase in the suction capability of the tube pump for the purpose of generating large negative pressure. This involves the problems such as those mentioned previously.
In order to generate a fast flow of ink, there is proposed a recording apparatus comprising a valve member disposed within an ink channel between the ink cartridge and the recording head for opening/closing the channel. When suction of ink is initiated by way of the capping member at the time of a cleaning operation, the valve member is closed. After negative pressure has been accumulated within an internal space of the capping member as a result of actuation of a suction pump, the valve member is opened to instantaneously increase the flow rate of ink within the recording head.
By means of this configuration, ink is instantaneously discharged with momentum to the inside of the capping member by the action of the accumulated negative pressure, thereby enabling discharge of air bubbles present in the channel, along with ink whose viscosity has been increased.
Since the valve member is opened while the suction pump remains idle, the ink discharged to the inside of the capping member remains frothed. The bubbles of ink adhere to the nozzle formation plane of the recording head and re-enter the nozzle orifices. This phenomenon results in a failure in the normal ejecting of ink droplets from the nozzle orifices, as well as printing of an image in mixed colors as a result of mixing of black ink and three color inks. In order to prevent the failures, there must be performed many repetitions of flushing operation, re-suction of ink while the negative pressure is reduced, and wiping operation.
Even when an attempt is made to forcibly remove ink clogging the nozzle orifices by means of only the accumulated negative pressure, the ink may not be readily removed if the adhesion of the ink to the nozzle orifices is relatively strong. The technical solution for increasing the suction capability of the pump is again sought, which in turn entails an increase in the size of the pump and the recording apparatus, as mentioned previously. Thus, means for solving the problems simultaneously is sought.
The present invention has been conceived in view of the technical problems described previously, and the first object of the present invention is to provide an ink jet recording apparatus capable of shortening suction time required for maintenance of a recording head and replenishment of ink, improving the suction capability of a pump unit, simplifying the pump unit, and being made compact overall.
The second object of the present is to provide a cleaning control method suitable for use with an ink jet recording apparatus having two recording heads.
The third object of the present invention is to provide an ink jet recording apparatus which eliminates clogging in a recording head and promotes discharge of air bubbles present in an ink channel without involvement of an increase in the size of the apparatus, as well as to provide a cleaning control method for use with the ink jet recording apparatus.
In order to achieve the first object, there is provided an ink jet recording apparatus comprising: at least one recording head having a face on which a plurality of nozzle orifices are formed, the recording head mounted on a carriage to be moved reciprocatively in the widthwise direction of a recording sheet; a capping device disposed in a non-print region of the recording head, the capping device including at least one cap unit for sealing the nozzle-formed surface of the recording head in cooperation with the movement of carriage; and a plurality of suction pumps for applying negative pressure in the interior space of the cap unit via suction tubes while the cap unit seals the nozzle-formed surface in cooperation with at least one drive source. The number of the suction pumps is at least equal to the number of the cap unit.
The apparatus may be configured that: a first recording head and a second recording head is mounted on the carriage; the capping device includes a first cap unit and a second cap unit provided for the first recording head and the second recording head respectively; and the plural suction pumps include a first suction pump and a second suction pump for applying negative pressure with respect to the first and second cap units respectively.
The respective suction pumps may cooperate with a single drive source.
The suction tubes may include a first suction tube for connecting the first cap unit and the first suction pump and a second suction pump for connecting the second cap unit and the second suction pumps which are different from each other in length or inner diameter.
The apparatus may be configured that: the cap unit includes a plurality of suction ports respectively communicating with the interior space thereof and connected to the respective suction pumps via the suction tubes; and the respective suction pumps perform the suction operation simultaneously.
The suction ports may be formed on an inner bottom portion of the cap unit and at one end portion in the longitudinal direction thereof. The suction ports may be arranged closely to one another. An air hole may be formed on an inner bottom portion of the cap unit and at the other end portion in the longitudinal direction thereof.
There may be provided in at least one of the suction tubes a valve member for opening/closing the same or a variable flow resistor for varying flow resistance thereof.
The apparatus may be configured that: the capping device includes a plurality of cap units; each of the cap units includes a suction port communicating with the respective interior space thereof; and each of the suction tubes connected to the respective suction ports has a junction portion for combining tubes connected to the respective suction pumps which perform the suction operation simultaneously.
The apparatus may be configured that: the capping device includes a plurality of cap units; each of the cap units includes a suction port communicating with the respective interior space thereof; and the suction tubes includes a first junction portion for combining subtubes connected to the respective suction ports and a second junction portion connected to the first junction portion for combining subtubes connected to the respective suction pumps which perform the suction operation simultaneously.
The subtubes connected to the respective suction pumps may be substantially the same in length. If necessary, the subtubes connected to the respective suction pumps may be different from each other in length or inner diameter. The subtubes connected to the respective suction ports may be different from each other in length or inner diameter.
There may be provided in at least one of the subtubes connected to the respective suction pumps a valve member for opening/closing the same or a variable flow resistor for varying flow resistance thereof.
The subtubes connected to the respective suction ports and the tubes connected to the respective suction pumps may be made of different materials.
The subtubes connected to the respective suction ports may be made of a material having high gas-barrier characteristic.
The recording head, which is sealed by the cap unit having shorter or thicker suction tube, may have larger number of the nozzle orifices.
The recording head for ejecting ink most susceptible to an increase in viscosity may be sealed by the cap unit having shorter or thicker suction tube.
There may be provided in at least one of the subtubes connected to the respective suction ports a valve member for opening/closing the same or a variable flow resistor for varying flow resistance thereof.
The subtube in which the valve member or the variable flow resistor is provided may be connected to a cap unit for sealing a recording head having relatively smaller number of nozzle orifices or a recording head for ejecting ink most susceptible to an increase in viscosity.
Each of the suction pumps may include: a frame body having a semicircular support face for supporting one of the suction tubes therealong; a wheel body rotated by the drive source in the frame body; and a plurality of rollers rotatably provided on the wheel body for squeezing the suction tube supported on the support surface. The rollers squeeze the suction tubes so as to become out of phase in the rotation direction of the wheel body with one another from the suction pump to the suction pump.
The plural suction pumps may be composed of a first suction pump and a second suction pump. The frame bodies of the first and second suction pumps are attached with each other so as to the central axis of the wheel bodies are made coincident with each other. The rollers squeeze the suction tubes so as to be 90xc2x0 out of phase in the rotation direction of the wheel body with one another from the first suction pump to the second suction pump. Outlets of the plural suction pumps may be lead to different waste-ink tanks.
The apparatus may further comprise means for counting the amount of ink flowing into the waste-ink tanks.
The counting means may count accumulately the amount of ink by selectively use of parameters specified according to respective ink suction operation modes.
The apparatus may further comprise: means for indicating whether the amount of ink counted by the counting means reaches for a predetermined value; and means for deactivating the apparatus when the amount of ink counted by the counting means reaches for a predetermined value.
Waste fluid absorbing members disposed in the respective waste-ink tanks are substantially the same in size. If necessary, the fluid absorbing members may be different from each other in size.
The counting means may be provided for each of the waste-ink tanks.
In order to achieve the second object, there is provided a cleaning control method for use with an ink jet recording apparatus comprising an elastic wiping blade abutted against the nozzle-formed faces of the first and second recording heads for wiping away ink adhering thereto, the method comprises the steps of: moving the carriage so the wiping blade as to wipe away ink adhering to the nozzle-formed face of the first recording head; stopping the carriage at a position where the wiping blade is situated between the first and second recording heads; waiting for the wiping blade to elastically restore to the original state thereof; and moving the carriage so the wiping blade as to wipe away ink adhering to the nozzle-formed face of the second recording head.
In order to achieve the second object without adopting the above method, the above apparatus discussed with regard to the first object may further comprise: an elastic wiping blade abutted against the nozzle-formed faces of the first and second recording heads for wiping away ink adhering thereto; and a spacer disposed between the first and second recording head so as to be touched by the wiping blade. The spacer may be made of a water-absorbing material. The apparatus may further comprise an absorber made of a water-absorbing material, and disposed between the first and second cap units so as to be brought into contact with the spacer while the nozzle-formed faces of the first and second recording heads are sealed by the first and second cap units.
In the ink jet recording apparatus employing the foregoing cleaning control method, the interior space of the cap units is evacuated by means of a plurality of suction pumps which simultaneously perform suction operation. As a result, the suction capability of the recording heads can be improved, and the ink, which is stored in the recording heads and whose viscosity has been increased, and air bubbles can be efficiently discharged. Accordingly, high-grade print quality of the recording apparatus can be ensured.
In this case, a tube pump which squeezes a tube by means of nipping action of a roller is used as the suction pump. As a result, the suction pumps can be connected by linearly connecting the drive shafts of the tube pumps in tandem, thereby reducing the volume occupied by the plurality of pumps.
Thus, the recording apparatus can be made compact as a whole. Further, the loads exerted on the pumps can be averaged by arranging the pumps such that the rollers squeeze the tubes such that the rollers come out of phase with one another from pump to pump in the direction of rotation of the pump wheel. Consequently, a motor having a large output rating is not required to be used as a drive source. This also contributes to a reduction in the size of the overall recording apparatus.
Valve member capable of opening or closing a suction channel, as needed, or a variable flow register capable of changing the resistance of the suction channel is disposed in the suction channels connected to the plurality of suction pumps. In a suction mode which does not require evacuation of a large amount of ink from the recording head, the amount of ink to be discharged can be controlled. As a result, the amount of ink supplied to the waste-ink tank can be reduced, thereby extending the interval for maintenance of the waste-ink tank and resulting in a reduction in consumption of the ink stored in an ink cartridge.
Further, so long as the recording apparatus is provided with means for counting the amount of ink supplied to the waste-ink tank, and an indication is made when the count made by the counting means exceeds a preset threshold value, an overflow of ink from the waste-ink tank can be prevented, thereby urging the user to perform maintenance of the waste-ink tank.
In order to achieve the third object, the above apparatus may further comprise: an ink reservoir for supplying ink to the recording head via a channel; a valve member provided in the channel, the valve member opened when the negative pressure is sufficiently accumulated within the interior space of the cap unit; at least two suction ports formed on the cap unit so as to be spaced apart from each other and connected to the respective suction pumps via the suction tubes; and control means for opening/closing the valve member and for driving the suction pumps either selectively or simultaneously.
The suction ports may be formed on a bottom face of the cap unit so as to be situated at both ends of a row of nozzle orifices for jetting ink most susceptible to an increase in viscosity while the nozzle-formed face of the recording head is sealed by the cap unit.
According to the present invention, there is also adopted a cleaning control method for use of the above apparatus, comprising the steps of: opening the valve member; driving the suction pumps simultaneously; closing the valve member; driving the suction pumps selectively; driving the suction pumps simultaneously; and opening the valve member. The order of the simultaneous drive and the selective drive while the valve member is opened may be interchanged.
The suction operation of the suction pumps may be continued for a predetermined time period even after the final step of opening the valve members.
The apparatus may comprise a plurality of ink reservoirs, channels and valve members.
According to the present invention, there is also adopted a cleaning control method for use of the above apparatus, comprising the steps of: opening the valve members; driving the suction pumps simultaneously; closing valve members other than a valve member for a row of nozzle orifices for ejecting ink most susceptible to an increase in viscosity; driving the suction pumps simultaneously; driving the suction pumps selectively; and opening the closed valve members. The order of the simultaneous drive and the selective drive while the valve member is opened may be interchanged.
The suction operation of the suction pumps may be continued for a predetermined time period even after the final step of opening the valve members.
The apparatus may be configured so as to further comprise: an ink reservoir for supplying ink to the recording head via a channel; a first valve member provided in the channel, the valve member opened when the negative pressure is sufficiently accumulated within the interior space of the cap unit; at least two suction ports formed on the cap unit so as to be spaced apart from each other and connected to the respective suction pumps via the suction tubes; a second valve member provided in at least one of the suction tubes; and control means for opening/closing the second valve member and for simultaneously driving the suction pumps while the first valve member is closed.
The suction ports may be formed on a bottom face of the cap unit so as to be situated at both ends of a row of nozzle orifices for jetting ink most susceptible to an increase in viscosity while the nozzle-formed face of the recording head is sealed by the cap unit.
In the ink jet recording apparatus employing any one of the foregoing cleaning control methods, the carriage is moved to a non-print area (i.e., the home position) at a time during which cleaning operation is performed, and the nozzle-formed face of the recording head is sealed by means of the cap unit located in the home position.
The valve member disposed in the ink channel extending from the ink reservoir to the recording head is closed, and the suction pumps connected to the inlets formed in the cap unit are selectively actuated. Alternatively, the valve member located in the suction channels extending from the inlets to the suction pumps are opened and closed, whereby negative pressure selectively acts on the inlets formed so as to become apart from each other in the cap unit.
Consequently, negative pressure selectively acts on clogged nozzle orifices in the recording head from different directions, thus imparting vibration to ink solids present in the nozzle orifices. Alternately, ink actively comes into contact with the clogged nozzles as a result of flow of ink which migrates between the inlets formed in the capping member, thus promoting softening or dissolution of the ink solids.
After completion of the foregoing operation, the suction pumps are simultaneously actuated, so that negative pressure is accumulated. The valve member are opened in this state, and hence a fast ink flow can instantaneously arise in the ink channel. By means of the fast flow of ink, the solids that have already undergone vibration or have become softened can be removed. Further, air bubbles present in the ink channel can also be discharged by means of the fast ink flow, thereby recovering the functions of the recording head and maintaining high print quality of the recording apparatus.
Like in the previous case, a fast ink flow can be effected in the ink channel by means of accumulated negative pressure even by simultaneously actuating the suction pumps while the valve member disposed in the ink channels extending from the ink reservoir to the recording heads are closed, and by opening the valves while the suction pumps are selectively actuated. Simultaneously, the vibration is imparted to the ink flow, thereby promoting recovery of functions of the recording head.
In a case where a tube pump, for example, is used as the suction pump, the plurality of tube pumps are connected such that the drive shafts of the tube pumps are connected in tandem. Consequently, the volume occupied by the plurality of pumps can be reduced, thus preventing an increase in the size of the recording apparatus.